The present invention relates to a self-reducing agglomerate that includes slag from electric furnace steel production. It further relates to a method for using this slag as a fluxing agent introduced to slag resulting from a refining process using the agglomerates in the production of iron.
It is known to produce steel by refining in an electric furnace. In this practice, an electrode is positioned above the bath or charge within the furnace. An arc is generated between the electrode and the bath or charge to provide the heat necessary for the fining operation. Slag resulting from this operation is inherently rich in iron content. This prevents its use in the production of concrete and asphault, which are common sources for disposal of other steelmaking slags, such as those resulting from oxygen steelmaking operations.
Consequently, electric furnace steelmaking slag is normally discarded in industrial waste sites at relative high cost and no return benefit.
In accordance with the invention, there is provided a self-reducing agglomerate for use in a refining operation for the production of molten iron. This agglomerate comprises a particle mixture of an iron oxide containing material, a reductant, and a fluxing agent. The iron oxide containing material includes about 5 to 30% of slag from electric furnace steel production.
Preferably, the slag is present in an amount of about 8 to 20%.
Preferably, the slag has a maximum particle size of about 6 mm for briquettes and 1 mm for pellets.
In accordance with an additional practice of the invention, the agglomerates may be used in a refining process for producing iron wherein slag from electric furnace steel production is introduced to the slag resulting from the refining process to act as a fluxing agent for nonmetallics present in the self-reducing agglomerates.
The slag may be present in the agglomerates in an amount sufficient to adjust the binary bacicity of the slag resulting from the refining process to a value of about 1.1 minimum and about 1.5 maximum.
The invention uses steel plant slag evenly distributed in the mixture to be agglomerated, which may be in the form of pellets and in the form of briquettes or other geometric shapes acceptable for the agglomeration process and the subsequent refining process.
The agglomerate is comprised of fines of iron ore and/or industrial residue containing iron oxides and/or metallic iron, fines of carbonaceous materials in sufficient amounts to reduce all the oxidized metals being present, fluxing materials, binders and humidity forming a homogenous mixture of all the components.
Preferably in the method according to the invention, the mixture of the agglomerate is comprised by self-reducing agglomerates formed in pellets, briquettes or another geometric shape adequate for the process of agglomeration and of reducing/melting.
In the present invention, the electric steel plant slag may be employed as a secondary source of iron and as a fluxing material for the nonmetallic impurities of the other components of the agglomerate and to adjust the binary basicity of the final slag, resulting from the process of reducing/melting of the agglomerate, to a value equal to 1.1 or above, that is, the ratio CaO/SiO2=1.1.
As a source of iron, the steel plant slag allows a decrease in the use of conventional iron sources, proportionally to the iron contents thereof in the necessary amount as fluxing material and to adjust the basicity of the final slag.
As a fluxing material, the steel plant slag replaces materials such as lime, limestone, cement and similar materials, by providing the same technical performance and, in addition, great economic advantage, because it is an industrial waste that is rich in calcium, the main component required in fluxing materials. For this application there are employed contents from 5 to 30% in the mixture to be agglomerated.